All Animals Are Domesticated: Angron gives Persephone a Cthellean Cudbear (a purple-furred, bat winged carniverous carnivore larger than most space marines), having housebroken it for her.
The Alliance: The Eldar Treaty which was signed sometime after that Age of Heresy formally established an alliance between the Imperium and some of the Eldar Craftworld and Exotdite worlds. Not all the Eldar are a part of the treaty however with the militantly anti-human Craftworld of Biel-tan being among the most prominent of the hold outs. A similar alliance exists with the Tau Farsight Enclaves.
Sailor Terra's author is aware that the Velociraptors are smaller than depicted in Jurassic Park. There is an intention to eventually portray them that way, but forgets to.
There was a post where in a 'fan' was very upset and spouting conspiracy theories because Velociraptors don't have feathers. The exchange culminated in Sailor Terra throwing progressively longer tailed and more scaly chickens at the man, then manifesting a fluffy T-Rex baby in his arms. The fic takes place in the 80s, the same time Sailor Moon does, that Velociraptors had feathers was only discovered in 2007.
The Atoner: In some continuities, Horus and his legions, after being purified by a Moon Princess Hallation. They can never be forgiven, but they try to redeem themselves anyway, hunting down other traitors.
Awesomeness Is a Force: The Emperor could probably burn normal peoples' sanity by just being in the area if he didn't bother reigning in his psychic presence. The same goes for the physical part of the matter.
Badass Bureaucrat: The relatively rare Librarians of the World Eaters legion very rarely see battle since they're busy providing astropathic and navigational services. This doesn't mean that they aren't enthusiastically dangerous opponents given the chance though.
Badass Normal: Captain Edmynion, just an ordinary officer of the Imperial Guard. But he manages to win the love of the second most powerful human in the universe and saves Warmaster Horus's life with a Heroic Sacrifice
Batman Gambit: Alta and Corax deceive Alaitoc craftworld with a prophecy that without the help of a band of Eldar pirates the craftworld is doomed. This lures the pirates, the actual target, into a trap.
Battle Couple: Esin and Amphithoe, Tekhne and Perturabo, Ira and Magnus, Russ and Thora
Beware the Nice Ones: Serenity is the source of light and hope in the Imperium and one of the main reasons why it is a much better place than it is in canon. She believes so strongly in peace that she even tried to make peace with Tyranids when Hivefleet Behemoth invaded. However, when the Behemoth Hivemind responded by very definitively rejecting the very concept of peace, she responded with a psychic assault that left it completely terrified by the very idea that something could hurt it at the level.
Brain Bleach: The general reaction to seeing Sailor Horus, both by youma and rescuees alike.
Bring My Brown Pants: An assassin learns to his detriment that you do not try to harm Serenity's 'little' brothers when just her tone of voice terrifies him, and this is after getting set on fire by an irate Mars.
Cain and Abel: Several Lovehammer renditions of the Horus Heresy have Horus killing one or more of his siblings.
The Chew Toy: The entire cast of the Sailor Horus continuity. Particularly Nefer.
Cute and Psycho: "Sailor" Fulgrim, most likely as a side effect of being reclaimed from Slaanesh. His new mission in life is to kill all perverts. Unfortunately being a beautiful mancross dressing as a sailor senshi, he tends to generate a lot of them himself.
Doubles as Yandere when Ferrus Manus becomes involved.
Everything Is Even Worse With Sharks: When the Youma jumped out of the water to escape the fish Sailor Terra used "Pretty Sailor Solider Shark Attack" since the great white was capable of jumping out of the water to get the Youma.
Fictional Holiday: Emperor's Day is celebrated across the Imperium (although in some cases it's more associated with Malcador than the Emperor).
The World Eaters call it Recruiting Day but their celebrations do include roast poultry and crackers.
Angron has a five season cartoon series based loosely on his actual actions.
Fisher King: Seems to be invoked with the Emperor in the "Toy Soldiers" storyline. Sailor Terra was drawn forth into the 'canon' 40k verse by Beryl and bound into service via the tradition of "Sacred Marriage" with the Emperor. Simply known as "Terra" she is insane from the state of the world in 40k and has little personality in common with the Mamoru/Darien Shields Sailor Terra.
Flirty Stepsiblings: It's a common belief in the Imperium that Horus and Serenity are or were very very fond of each other despite being (adopted) siblings.
Four-Star Badass: Most of the Royal Family have armies under their command which doesn't stop them fighting on the frontlines.
Almost straight examples with the married Primarchs and Senshi. Jupiter is far from being short, but even a tall woman will look tiny next to a Primarch.
Innocent Fanservice Girl: When Angron is reborn as a girl in the Sailor Horus storyline, he cares little if someone can see up his skirt while fighting evil.
The Internet Is for Porn: The Martian global network consists of 40% porn. The Emperor assures them that this is completely to be expected that such happen spontaneously to such a network, and that Slaanesh isn't involved.
But it's icky wet fleshy sex! For the cyborg, flesh-hating Mechanicus this is layers of perversion and ew. Their own datasphere is trolling them.
IN NOMINE LUNA: Space Marines shout this occasionally. They have at least once also declared something like that they win battles during the night and fight for justice during the day. And it is seriously scary to their opponents.
"THE EMPEROR'S WRATH UPON THE BETRAYER!" was the retort of a thousand strong.
"The Wolves no longer howl at the Moon."
"LET THE DARK DESTROY THE DARK!"
"Brothers! I offer you the Astral Claws and Huron Blackheart, the Tyrant of Badab!"
Let's just say its so bad it is wonderful, and hilarious.
THE ANGRY ONE IS A FRIEND TO ALL CHILDREN!
Also Leman Russ: “Lo! Did the hero rise his mighty mop and clean the treacherous floor!” a thunderous roar sounded from the depths of the Imperial Palace.
Last of His Kind: After the destruction of Chogoris at the hands of rogue Space Marines, Jaghatai and the remnants of his family are this. Before the event, as befitting of a Khan, Jaghatai had 300+ wives, many children, and along with relatives, a family of over 1000 people. After the event, and the rest of the Age of Heresy, all he had remaining was ten people.
Lethal Chef: Serenity's attempts at cooking go as well as in canon.
Luke, I Am Your Father: Pretty much how finding a Primarch works, unless it's Serenity that makes first contact, which seems to be most of the time. Then again, those instances only mean that the Luke, I Am Your Father moment is temporarily delayed.
As an example, in Toy Soldiers Ferrus Manus fell to Nurgle, and Fulgrim lost most of his legion but they succeed in putting the Iron fists down, burning them on pyres. Horrifically repeating the mental denial that it wasn't, hadn't been his brother. This barely has time to sink in on the thread when the next ficbit goes up. They are resurrected as Llamas and Prinnies as they had been warned would happen. Purple Llamas. They are sent to petting zoos since they likely fell due to lack of hugs.
Morton's Fork: Fulgrim was warned about the sword on Laer. If he took it he'd be exposed to it, if he refused it they would know he had been warned.
Not Blood Siblings: Serenity and the Primarchs Alpharius and Omegon's realization of this upon meeting them is what sows the seeds of their suspicion towards her and the Senshi, and eventually, Omegon's fall.
Tomboyish Name: Russ and Thora's daughter Ulfhild. They were expecting a boy, so no female names were considered.
The Archivist notes that it was mostly Russ that was absolutely convinced that they where going to have a son, so Thora had to step in. Still, Ulfhild is named in honour of her father. Awww.
And none-the-less it is a female name, yay for the harshness of Nordic/Germanic languages, I suppose?
Troll: Malacador and the Imperial Family, mostly the male half. That and violence is how they bond. The Emperor is the biggest troll of them all.
Not anymore. Ruin as the personification of Entropy in the SM universe, with Cosmos (aka far, far, far future Serenity) personifying Order, has been inserted into the 40k universe. His entire existence is to troll other beings, except that he in turn is trolled by Cosmos. He trolls her back by killing her Senshi in ever-more inventive ways. Being thrown into the grim dark galaxy ironically mellowed him/it out a lot.
Some consider Ruin indicative of the OC bloat in Lovehammer. However, due to multiple continuities and the friendly posting atmosphere, this is not as much of a problem as keeping track of the many different continuities. Yes. The confused reader needs to troll back.
a Dark Eldar character known as Ruith not only trolls the imperium (his introduction has him announcing his intention to court Sailor Morta) , but has managed to use trolling and mindscrews as a alternative food source than teh typical Dark Eldar addiction to pain and torment.
Twin Switch: Alpharius and Omegon pull this occasionally with Omegon forcing a permanent one when he joins Lorgar and takes most of their legion with him.
Up to Eleven: Young Rogal Dorn's pillow forts, which involved the entire cushion contents of multiple wings of the family compound, plus some from the neighbors.
Utility Belt: Perturabo gave Tekhne one as a wedding anniversary. It is known to contain at least two pairs of earplugs and a holdout boltpistol.